Recording apparatus and recording method

ABSTRACT

A recording apparatus generates a first pulse (EQEFM signal) in accordance with recording data such as an EFM signal. A second pulse (first overdrive pulse) to be combined with substantially the leading edge of the first pulse is generated. A third pulse (end overdrive pulse) to be combined with substantially the trailing edge of the first pulse is generated. The first, second, and third pulses are combined to synthesize a driving pulse, and the driving pulse is supplied to a laser unit. At least one of the first, second, and third pulses is controlled so that one of the level and the pulse duration thereof is varied in accordance with the length of formed pits and lands.

This application is a divisional application of Ser. No. 09/650,929files on Aug. 29, 2000 now U.S. Pat. No. 6,614,739.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording apparatus and a recordingmethod for performing light modulation recording, that is, datarecording on a recording medium by a laser beam modulated by recordingdata.

2. Description of the Related Art

When performing light modulation recording on a recording medium such asan optical disk or the like, a laser emits light in pulses in order toperform thermal control for shaping a pit (mark) to be formed on thedisk.

Specifically, a pulse waveform as a driving pulse for driving the laseris arranged, and the level (peak value) during each pulse period iscontrolled, thereby controlling the laser power and the laserirradiation time.

For example, data is written on disk media in which data can be written,namely, CD-recordable (CD-R) which is CD-write once (CD-WO) andCD-rewritable (CD-RW), at data writing speeds of ×1, ×2, and ×4 speeds.Laser emission control in accordance with the writing speed is performedas shown in FIGS. 14 and 15. The ×1 speed corresponds to 1.2 to 1.4 m/s,which is achieved by rotating a disk in a constant linear velocity (CLV)mode.

FIG. 14 shows a driving pulse generated when writing at a ×1 writingspeed or a ×2 writing speed.

It is known that a CD system generates an EFM signal as recording data.The pulse duration of the EFM signal is specified within a range of 3 Tto 11 T, as shown in FIG. 14. The letter “T” corresponds to one channelclock period.

Based on the EFM signal, an equalized EFM signal (hereinafter referredto as an “EQEFM signal”) is generated, as shown in FIG. 14. The EQEFMsignal is used as a laser driving pulse.

In the example shown in FIG. 14, the EQEFM signal has a pulse whichbasically has a duration of (N−1)T compared with (N)T of the EFM pulse(in the drawing, θ=1 T).

For example, concerning the EFM signal having a pulse duration of 4 T,the EQEFM signal having a pulse duration of 3 T is generated. Concerningthe EFM signal having a pulse duration of 11 T, the EQEFM signal havinga pulse duration of 10 T is generated. With regard to the EFM signalhaving a pulse duration of 3 T, a period of α=0.13 T is added to thepulse duration of the EQEFM signal. The symbol “Pw” represents thewriting laser power.

The EQEFM signal corresponds to the laser emission level. Concerning theEFM pulse having a duration of (N)T, the EQEFM signal having a pulseduration of (N−1)T is generated. This is configured so in anticipationof a portion in which a pit is formed by thermal accumulationimmediately after the laser emission is stopped.

Therefore, the relationship between the EFM signal and the formed pits Pand lands L is such that the pulse duration is associated with the pitlength and the land length, as shown in FIG. 16.

FIG. 15 shows a driving pulse generated when writing at a ×4 writingspeed.

In the example shown in FIG. 15, the EQEFM signal has a pulse whichbasically has a duration of (N−0.5)T with respect to the EFM pulsehaving a duration of (N)T (in the drawing, θ=0.5 T). For example,concerning the EFM signal with a pulse duration of 4 T, the EQEFM signalhaving a pulse duration of 3.5 T is generated.

In this case, an increased power portion expressed by ΔP is added toperiod ODT at the leading edge of the pulse. Hereinafter, the increasedpower portion or a pulse for forming the increased power portion isreferred to as an overdrive pulse.

FIG. 17 shows pits and lands formed by a laser which is driven to emitlight based on a driving pulse generated by the method shown in FIG. 14.FIG. 18 shows pits and lands formed by a laser which is driven to emitlight based on a driving pulse generated by the method shown in FIG. 15.

FIGS. 17 and 18 show the laser power controlled by driving pulsesgenerated based on the EFM signal shown in FIG. 16. The symbol “Pw”represents the writing laser power, and the symbol “Pr” represents thereading laser power. FIG. 17 and 18 show the formed pits P and lands L.

Referring to FIGS. 17 and 18, period A and period B each indicate adelay from the start of the laser beam emission until the formation ofthe pit P starts. Period a and period b each indicate a delay from thetermination of the laser emission until the formation of the pit P iscompleted.

Recently, recording rates have been increased. Concerning CD-R andCD-RW, the recording rates have been further increased. For example,recording at a ×8 speed has been achieved.

Upon recording at the ×8 speed, when the laser power is controlled bythe method shown in FIG. 14 or by the method shown in FIG. 15,intersymbol interference occurs, and jitter of the recording dataincreases. In the worst case, the recording data cannot be read.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to implement laserpower control so that appropriate recording is performed at a fastrecording rate.

According to one aspect of the present invention, there is provided arecording apparatus. The recording apparatus includes a laser unit forperforming laser beam irradiation with a supplied driving pulse to forma recording data row on a recording medium. The data row is formed ofpits and lands, in which the lands are between the pits and the pits arebefore and after the lands. A driving pulse generator generates a firstpulse in accordance with recording data, a second pulse to be combinedwith the leading edge of the first pulse, and a third pulse to becombined with the trailing edge of the first pulse. The driving pulsegenerator synthesizes the driving pulse by combining the first, second,and third pulses. A pulse generation controller controls at least one ofthe first, second, and third pulses generated by the driving pulsegenerator so that one of the level and the pulse duration thereof isvaried in accordance with the length of at least one of the formed pitsand lands.

Preferably, the pulse generation controller variably sets, in accordancewith a predetermined recording condition, the level of each of thesecond and third pulses.

The pulse generation controller may variably set, in accordance with apredetermined recording condition, the pulse duration of each of thesecond and third pulses within a range of 0 T to 3 T.

The pulse generation controller may variably set, in accordance with thelength of at least one of the pit and the land immediately formedbefore, the pulse duration of at least one of the first, second, andthird pulses.

The recording apparatus may further include a detector for detecting thelength of the land immediately formed before the formed pit. The pulsegeneration controller may vary the pulse duration of the first pulse inaccordance with the detected land length.

The detector may detect the length of the formed pit. The pulsegeneration controller may vary the pulse duration of the first pulse inaccordance with the detected pit length.

The detector may detect the length of the land formed immediately afterthe formed pit. The pulse generation controller may vary the pulseduration of the first pulse in accordance with the detected land length.

The recording apparatus may further include a switch for switching theoperation of the driving pulse generator so that at least one of thefirst, second, and third pulses generated by the driving pulse generatoris not output. The pulse generation controller may control the switch inaccordance with a speed at which the recording data row is formed on therecording medium.

The recording medium may be a write once optical disk. The pulsegeneration controller may control the switch so that the third pulse isnot output when the optical disk is rotated at a linear velocity notgreater than a four-times speed of a reference linear velocity.

According to another aspect of the present invention, there is provideda recording method. The recording method includes a generating step ofgenerating a first pulse in accordance with recording data, a secondpulse to be combined with the leading edge of the first pulse, and athird pulse to be combined with the trailing edge of the first pulse, inwhich one of the level and the pulse duration is varied in accordancewith the length of at least one of formed pits and lands. In asynthesizing step, a driving pulse is synthesized by combining thefirst, second, and third pulses. In a forming step, a recording data rowis formed on a recording medium by performing laser beam irradiationusing the driving pulse. The recording data row is formed of the pitsand the lands, in which the lands are between the pits and the pits arebefore and after the lands.

The recording method may further include a control step of controlling,in the generating step of generating the first, second, and thirdpulses, the second and third pulses not to be generated in accordancewith a speed at which the recording data row is formed on the recordingmedium.

Accordingly, thermal interference between codes (pits and lands) to berecorded is reduced. When recording at a fast recording rate, such as a×8 speed, appropriate pits and lands are formed in which a sufficientread margin is obtained. A reduction in recording jitter improves thequality of recording data. Recording in accordance with a recordingenvironment is performed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a recording and reading apparatus accordingto an embodiment of the present invention;

FIG. 2 is a block diagram of a writing laser power control system of theembodiment;

FIG. 3 includes illustrations of writing laser patterns and drivingpulses of the embodiment;

FIG. 4 is an illustration of an example of a writing laser pattern ofthe embodiment;

FIG. 5 is an illustration of another example of a writing laser patternof the embodiment;

FIG. 6 is an illustration of another example of a writing laser patternof the embodiment;

FIG. 7 is an illustration of another example of a writing laser patternof the embodiment;

FIG. 8 is an illustration of another example of a writing laser patternof the embodiment:

FIG. 9 is an illustration of another example of a writing laser patternof the embodiment;

FIG. 10 is a graph showing the writing laser power and pit jittercharacteristics obtained by a cyanine-based disk of the embodiment;

FIG. 11 is a graph showing the writing laser power and land jittercharacteristics obtained by the cyanine-based disk of the embodiment;

FIG. 12 is a graph showing the writing laser power and pit jittercharacteristics obtained by a phthalocyanine-based disk of theembodiment;

FIG. 13 is a graph showing the writing laser power and land jittercharacteristics obtained by the phthalocyanine-based disk of theembodiment;

FIG. 14 illustrates a conventional laser driving pulse generatingmethod;

FIG. 15 illustrates another conventional laser driving pulse generatingmethod;

FIG. 16 illustrates the relationship between an EFM signal and pits andlands;

FIG. 17 illustrates the laser power and pits and lands obtained by usingthe conventional laser driving pulse generating method shown in FIG. 14;and

FIG. 18 illustrates the laser power and pits and lands obtained by usingthe conventional laser driving pulse generating method shown in FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be understood from the following descriptionof a disk drive according to an embodiment which conforms to CD-R andCD-RW.

CD-R is a write-once medium in which organic dye is used to form arecording layer. CD-RW is a medium in which data can be rewritten byusing a phase change technique.

Referring to FIG. 1, the structure of the disk drive according to theembodiment for reading and writing data to a disk such as a CD-R or aCD-RW disk is described.

In FIG. 1, a disk 90 is a CD-R or a CD-RW disk. Also, a CD-DA or aCD-ROM as the disk 90 can be read.

The disk 90 is mounted on a turntable 7. When reading or writing, theturntable 7 is rotated and driven by a spindle motor 1 at a constantlinear velocity (CLV) or a constant angular velocity (CAV). An opticalpick-up 1 reads pit data (phase change pits or pits formed by organicdye change (reflectivity change)) on the disk 90. In the case of theCD-DA or the CD-ROM, the pits are embossed pits.

In the pick-up 1, a laser diode 4 used as a laser light source, a photodetector 5 for detecting reflected light, an objective lens 2 used at anoutput end of the laser beam, and an optical system (not shown) forirradiating a disk recording surface with the laser beam through theobjective lens 2 and for guiding the reflected light to the photodetector 5 are formed.

Also, a monitor detector 22 for receiving part of the light output fromthe laser diode 4 is provided.

The objective lens 2 is movably retained in the tracking direction andin the focusing direction by a two-axis mechanism 3.

The entire pick-up 1 is movable in the radial direction of the disk by asled mechanism 8.

The laser diode 4 in the pick-up 1 is driven to emit light by a drivingsignal (driving current) from a laser driver 18.

Light information reflected from the disk 90 is detected by the photodetector 5. In accordance with the quantity of received light, thedetected light information is supplied as an electrical signal to aradio frequency (RF) amplifier 9.

The RF amplifier 9 includes a current-voltage converting circuit inaccordance with the output current from a plurality of light receivingelements as the photo detector 5, a matrix arithmetic/amplifier circuit,and the like. A necessary signal is generated by matrix arithmeticprocessing. For example, an RF signal used as read data, and a focuserror signal FE and a tracking error signal TE used to perform servocontrol are generated.

The read RF signal output from the RF amplifier 9 is supplied to abinarization circuit 11, and the focus error signal FE and the trackingerror signal TE are supplied to a servo processor 14.

A groove to be used as a guide on a recording track is formed in advanceon the CD-R or CD-RW disk 90. The groove wobbles (meanders) due to asignal in which time information indicating an absolute address on thedisk is FM-modulated. When writing, it is possible to perform trackingservo based on the groove information, and to obtain the absoluteaddress based on wobbling information WOB of the groove. The RFamplifier 9 extracts the wobbling information WOB by the matrixarithmetic processing, and supplies the wobbling information WOB to anaddress decoder 23.

The address decoder 23 demodulates the supplied wobbling informationWOB, thus obtaining the absolute address. The absolute address issupplied to a system controller 10.

By supplying the groove information to a phase-locked loop (PLL)circuit, information on the rotation speed of the spindle motor 6 isobtained. Comparison between the obtained rotation speed information andreference speed information generates a spindle error signal SPE, andthe spindle error signal SPE is output.

The read RF signal obtained by the RF amplifier 9 is binarized by thebinarization circuit 11, thereby forming a so-called eight to fourteenmodulation (EFM) signal. The EFM signal is supplied to anencoder/decoder 12.

The encoder/decoder 12 includes a function region used as the decoderwhen reading and a function region used as the encoder when writing.

When reading, the encoder/decoder 12 performs EFM modulation, crossinterleaved Reed-Solomon code (CIRC) error correction, de-interleaving,and CD-ROM decoding as decoding processing. Hence, read data which isconverted into CD-ROM format data is obtained.

Also, the encoder/decoder 12 extracts a sub-code from data read from thedisk 90, and supplies a table of contents (TOC) and address informationas the sub-code (Q data) to the system controller 10.

Furthermore, the encoder/decoder 12 generates a read clock insynchronism with the EFM signal by PLL processing. Based op the readclock, the encoder/decoder 12 performs the above decoding processing.The rotation speed information of the spindle motor 6 is obtained basedon the read clock, and the rotation speed information is compared withthe reference speed information. Hence, the spindle error signal SPE isgenerated and output.

When reading, the encoder/decoder 12 stores the data decoded as above ina buffer memory 20.

The data buffered in the buffer memory 20 is read, transferred, andoutput as a read output from the drive.

An interface 13 is connected to an external host computer 80, andcommunicates recording data, read data, and various commands with thehost computer 80. In fact, an interface conforming to the small computersystem interface (SCSI) or the advanced technology attachment packetinterface (ATAPI) is adopted. When reading, the decoded read data storedin the buffer memory 20 is transferred and output to the host computer80 through the interface 13.

Read commands, write commands, and other signals from the host computer80 are supplied to the system controller 10 through the interface 13.

In contrast, when writing, recording data such as audio data and CD-ROMdata is transferred from the host computer 80. The recording data istransmitted from the interface 13 to the buffer memory 20, and therecording data is buffered in the puffer memory 20.

In this case, the encoder/decoder 12 performs, as encoding processing ofthe buffered recording data, encoding of CD-ROM format data as CD formatdata when the supplied data is the CD-ROM format data, CIRC encoding,interleaving, sub-code addition, and EFM modulation.

The EFM signal obtained by the encoding processing performed by theencoder/decoder 12 undergoes processing referred to as writeequalization which is performed by a recording signal generator 21.Subsequently, the processed EFM signal is transmitted as write dataWDATA to the laser driver 18. The recording signal generator 21generates and outputs an EQEFM signal, a first overdrive pulse, and anend overdrive pulse as the write data WDATA. This is described in thefollowing description with reference to FIG. 2.

The laser driver 18 converts the EQEFM signal, the first overdrivepulse, and the end overdrive pulse, which are supplied as the write dataWDATA, into current signals. The current signals are combined and sentto the laser diode 4, thereby driving the laser diode 4 to emit light.Accordingly, pits (phase change pits or dye change pits) in accordancewith the EFM signal are formed on the disk 90.

An auto power control (APC) circuit 19 monitors the laser output powerbased on the output power of the monitor detector 22 and controls theoutput power of the laser to remain constant independent of temperatureand the like. A desired value of the laser output power is supplied fromthe system controller 10. The laser driver 18 is controlled so that thelevel of the laser output power becomes the desired value.

Based on the focus error signal FE and the tracking error signal TE fromthe RF amplifier 9, the spindle error signal SPE from theencoder/decoder 12 or the address decoder 20, and the like, the servoprocessor 14 generates various servo driving signals including focus,tracking, sled, and spindle driving signals, thereby performing servooperations.

Specifically, a focus driving signal FD and a tracking driving signal TDare generated in accordance with the focus error signal FE and thetracking error signal TE, respectively. The focus driving signal FD andthe tracking driving signal TD are supplied to a two-axis driver 16. Thetwo-axis driver 16 drives a focus coil and a tracking coil in thetwo-axis mechanism 3 in the pick-up 1. Hence, a tracking servo loop anda focus servo loop are formed by the pick-up 1, the RF amplifier 9, theservo processor 14, the two-axis driver 16, and the two-axis mechanism3.

In response to a track jump command from the system controller 10, thetracking servo loop stops. A jump driving signal is output to thetwo-axis driver 16, thus causing the two-axis driver 16 to perform atrack jump operation.

The servo processor 14 supplies a spindle driving signal generated inresponse to the spindle error signal SPE to a spindle motor driver 17.In response to the spindle driving signal, the spindle motor driver 17supplies, for example, a three-phase driving signal to the spindle motor6, thus causing the spindle motor 6 to rotate at the CLV or the CAV. Inresponse to a spindle kick/brake control signal from the systemcontroller 10, the servo processor 14 generates the spindle drivingsignal, thus causing the spindle motor driver 17 to activate, stop,accelerate, or decelerate the spindle motor 6.

Based on, for example, a sled error signal obtained as a low-frequencycomponent of the tracking error signal TE and on access executioncontrol by the system controller 10, the servo processor 14 generates asled driving signal, and the sled driving signal is supplied to a sleddriver 15. The sled driver 15 drives the sled mechanism 8 in response tothe sled driving signal. The sled mechanism 8 has a mechanism (notshown) including a main shaft for retaining the pick-up 1, a sled motor,a transmission gear, and the like. The sled driver 15 drives the sledmotor 8 in response to the sled driving signal, thus causing the pickup1 to perform necessary sliding.

Various operation of the servo system and the read/write system iscontrolled by the system controller 10 formed by a micro computer.

The system controller 10 performs various processing in response tocommands from the host computer 80.

For example, when a read command requesting the transfer of certain datarecorded on the disk 90 is supplied from the host computer 80, seekoperation control aiming at the designated address is performed.Specifically, a command is issued to the servo processor 14, and thepick-up 1 gains access to the address designated by a seek command.

Subsequently, operation control required to transfer the data in thedesignated data segment to the host computer 80 is performed.Specifically, the data is read from the disk 90, and the read data isdecoded and buffered, thereby transferring the data.

When a write command is issued from the host computer 80, the systemcontroller 10 moves the pick-up 1 to an address at which writing is tobe performed. The encoder/decoder 12 encodes the data transferred fromthe host computer 80, as described above, and the EFM signal is thusgenerated.

When the write data WDATA is supplied from the recording signalgenerator 21 to the laser driver 18, as described above, recording isperformed.

FIG. 2 shows a section of the disk drive for generating a laser drivingpulse which is generated when writing.

When writing, the EFM signal is supplied from the encoder/decoder 12 tothe recording signal generator 21. The recording signal generator 21includes a pit/land length detecting circuit 31, an end pulse generatingcircuit 32, a first pulse generating circuit 33, and an EQEFM generatingcircuit 34.

Based on the EFM signal, the EQEFM generating circuit 34 generates anEQEFM signal V1 which is at a predetermined level and which has apredetermined pulse width.

The first pulse generating circuit 33 generates a first overdrive pulseV2 which is to be added to substantially the leading edge of the laserdriving pulse.

The end pulse generating circuit 32 generates an end overdrive pulse V3which is to be added to substantially the trailing edge of the laserdriving pulse.

The end pulse generating circuit 32, the first pulse generating circuit33, and the EQEFM generating circuit 34 generate the signals V1, V2, andV3, respectively, each having a pulse width in accordance with the pulseduration of the EFM signal. Based on the pulse duration of the currentEFM signal and the pit length and the land length immediately beforeeach pulse which are detected by the pit/land length detecting circuit31, the pulse width and the pulse level (voltage level) are variablycontrolled.

Switches SW1, SW2, and SW3 are switching circuits forenabling/disenabling the EQEFM signal V1, the first overdrive pulse V2,and the end overdrive pulse V3, respectively. The switches SW1, SW2, andSW3 are controlled by the system controller 10. In response to a writecommand or a mode setting command from the host computer 80, the systemcontroller 10 determines at which speed the recording data transferredfrom the host computer 80 is to be recorded. The system controller 10changes over the switches SW1, SW2, and SW3 in accordance with therequested writing speed. For example, when writing at a ×1 writing speedor a ×2 writing speed, as in the driving pulses shown in FIGS. 14 and17, the switches SW2 and SW3 are turned off so that the first overdrivepulse V2 and the end overdrive pulse V3 are not added to the EQEFMsignal V1. Hence, the first pulse generating circuit 33 and the endpulse generating circuit 32 are disenabled. When the requested writingspeed is a ×4 speed, only the switch SW3 is turned off so that, as inthe driving pulses shown in FIG. 15 and 18, the end overdrive pulse V3is not output. When recording data at an ×8 speed which is newlyachieved in the present invention, the switches SW1, SW2, and SW3 areturned on, thereby outputting the driving pulse shown in FIGS. 4 to 9.

Specific examples of pulses as the signals V1, V2, and V3 are describedin the following description.

The EQEFM signal V1, the first overdrive pulse V2, and the end overdrivepulse V3 are converted into current signals i1, i2, and i3,respectively, by the laser driver 18, i.e., by voltage/currentconverting circuits 37, 36, and 35, respectively.

An adding circuit 38 adds the current signals i1, i2, and i3 to generatea driving current i, which is to be supplied to the laser diode 4.

In this embodiment, a control signal is input from the system controller10 to the voltage/current converting circuits 37, 36, and 35. Dependingon the disk rotation speed (linear velocity with respect to a track)when writing, the length of a pit to be recorded, the material of therecording layer (dye film) used in the disk 90, the ambient temperature,and the like, the level (amplitude) of each pulse is changed. In thiscase, the control signal and a parameter are input from the systemcontroller 10. Therefore, the levels (amplitude) of the signals V1, V2,and V3 are individually controlled by the parameters input to thevoltage/current converting circuits 37, 36, and 35. In this embodiment,the voltage/current converting circuits 37, 36, and 35 each have a leveladjusting function. Alternatively, a separate level adjusting circuitcan be provided at a preceding stage or a subsequent stage of each ofthe voltage/current converting circuits 37, 36, and 35.

The laser power controlled by the above structure is described below.

FIG. 3 shows examples of the end overdrive pulse V3 (ODP_END), the firstoverdrive pulse V2 (ODP_FIRST), and the EQEFM signal V1.

These signals V1, V2, and V3 are converted into current values, and thecurrent values are added to give the driving current i. The drivingcurrent i is used to output the laser power, as shown in FIG. 3.Specifically, power generated by the first overdrive pulse is added tothe leading edge of the EQEFM signal, and power generated by the endoverdrive pulse is added to the trailing edge. The symbol “Pr” indicatesa reading laser level, the symbol “Pw” indicates a writing laser level,and the symbol “Pod” indicates a laser level obtained by the overdrivepulses.

Since the output laser power of the laser diode 4 is controlled asabove, pits P and lands L are formed on the disk 90, as shown in FIG. 3.

Referring to FIG. 3, period C indicates a delay from the start of laserbeam emission until the formation of the pit P starts. Period cindicates a delay from the termination of the laser beam emission untilthe formation of the pit P is completed.

Period C and period c are shorter than period A and period B and perioda and period b shown in FIGS. 17 and 18. This indicates that, even whenwriting at a fast rate, pits and lands which accurately conform to theEFM signal are formed in this embodiment.

According to the embodiment, the end overdrive pulse and the firstoverdrive pulse are added to the EQEFM signal to generate the drivingcurrent i. The EQEFM signal, the end overdrive pulse, and the firstoverdrive pulse which are generated by the recording signal generator 21are controlled so that the level and the pulse duration thereof arechanged in accordance with corresponding recording conditions and thepit length and the land length before and after each pulse detected bythe pit/land length detecting circuit 31. In addition, the pulse widthis arbitrarily and variably set by the system controller 10 inaccordance with each of 3 T to 11 T.

Specifically, the pulse width is obtained such that, for the EFM pulsehaving a width of (N)T, a signal which basically has a pulse width of(N−X(N))T is generated.

In other words, values “X3” to “X11” used to set the pulse width of theEQEFM signal are arbitrarily set in accordance with the pulses eachhaving a corresponding width of 3 T to 11 T.

For example, FIG. 3 is associated with the EFM signal shown in FIG. 16.Referring to FIG. 3, concerning the EFM signal having a pulse durationof 3 T, the EQEFM signal having a pulse width of (3−X3)T is generated.Concerning the EFM signal having a pulse duration of 11 T, the EQEFMsignal having a pulse duration of (11−X11)T is generated.

Specifically, the pulse width is controlled in accordance with adifference in the pulse width (difference in thermal storage on arecording track caused by a difference in laser irradiation periods).Accordingly, pits and lands which suitably conform to the EFM signal areformed.

For example, it is arranged that X3 to X11 take values 0.25 to 0.2,respectively.

The first overdrive pulse and the end overdrive pulse are added to theEQEFM signal. For example, various patterns as shown in FIGS. 4 to 9 areemployed as waveform patterns (laser output level control patterns) tobe combined. Referring to FIGS. 4 to 9, the symbol “L1” indicates apulse width of the first overdrive pulse, and the symbol “L2” indicatesa pulse width of the end overdrive pulse.

Referring to FIG. 4, L1=L2. In this example, the rising of the firstoverdrive pulse and the falling of the end overdrive pulse are insynchronism with the EQEFM signal.

Referring to FIG. 5, L1<L2. In this example, the rising of the firstoverdrive pulse and the falling of the end overdrive pulse are insynchronism with the EQEFM signal.

Referring to FIG. 6, L1>L2. In this example, the rising of the firstoverdrive pulse and the falling of the end overdrive pulse are insynchronism with the EQEFM signal.

Referring to FIG. 7, L1=L2. In this example, the rising of the firstoverdrive pulse occurs prior to the EQEFM signal, and the falling of theend overdrive pulse occurs subsequently to the EQEFM signal.

Referring to FIG. 8, L1<L2. In this example, the rising of the firstoverdrive pulse is in synchronism with the EQEFM signal, and the fallingof the end overdrive pulse occurs subsequently to the EQEFM signal.

Referring to FIG. 9, L1>L2. In this example, the rising of the firstoverdrive pulse occurs prior to the EQEFM signal, and the falling of theend overdrive pulse is in synchronism with the EQEFM signal.

In each of the above examples, a laser beam emission pattern indicatedby LD optical output is obtained.

Alternatively, patterns other than the above may be used.

Usage of each pattern, particularly, periods L1 and L2, is set inaccordance with the pit length or the land length immediately before andafter each pulse which is detected by the pit/land length detectingcircuit 31. For example, when the preceding land segment is long, L1 isprolonged. In contrast, when the preceding land segment is short, L1 isshortened.

Specifically, the laser drive pattern is controlled in accordance withvariations in the thermal storage caused by the pit length and the landlength.

Periods L1 and L2 can be varied within a range of 0 T to 3 T.

Although not shown, the levels (voltage values) of the end overdrivepulse and the first overdrive pulse may be changed in accordance withthe pit length or the land length immediately before and after eachpulse, as in the case of the above L1 and L2.

Specifically, heat accumulated in the disk 90 is determined based on thequantity of the laser beam and the period. By changing the quantity ofthe laser beam, an appropriate laser drive pattern can be configured inaccordance with variations in the thermal storage caused by the pitlength and the land length.

For example, the level Pod shown in FIG. 3 may be changed by an increaseof 20%, an increase of 25%, and an increase of 30% over the writinglaser power Pw.

When writing, the CD-R disk 90 is rotated at a ×8 speed. At the sametime, a parameter is supplied when generating each pulse. This isdescribed with reference to the waveform patterns shown in FIG. 6 by wayof example.

The EQEFM signal has a pulse width of (N−0.25)T. The first overdrivepulse has a pulse duration of L1 and the end overdrive pulse has a pulsewidth of L2. When the length of a land immediately formed before orafter the first overdrive pulse or the end overdrive pulse is 8 T,L1=1.75 T and L2=1T. The levels (amplitude) of these pulses areapproximately 30% greater than the level of the EQEFM signal. The pulsewidth of the first overdrive pulse is varied by setting the parameterfor the signal generator 21 by the system controller 10 in accordancewith the pit length (3 T to 11 T) to be recorded and the land length (3T to 11 T) formed immediately before and after the pulse. Specifically,the land length immediately before the pulse may take nine differentvalues. The pit length to be recorded may take nine different values.The land length immediately after the pulse may take nine differentvalues. Taken all together, the parameter has 729 differentcombinations. For example, when L1=1.75 T and the pit length to berecorded is 4 T, the parameter is set to 1.05 T. When the pit length tobe recorded ranges from 5 T to 11 T, the parameter is set to 0.35 T. Inaddition, in accordance with the land length before the pulse, −0.2 T to+0.2 T is added. For example, when L1=1.75 T is used as a referencevalue, the parameter may take a value ranging form 1.55 T to 1.95 T.

Actually, the pulse width and the pulse level are adjusted depending onthe material of the disk 90 (material of the dye film), themanufacturer, the recording linear velocity, the recording rate, and thecharacteristics of the optical system of the pick-up 1.

A difference in thermal reaction is caused by a different material ofthe dye film. When writing, it is advantageous to determine the type andthe manufacturer of the mounted disk 90 and to adjust the pulse widthand the pulse level. The operating environment while writing, such asthe recording linear velocity and the recording rate, can be transferredfrom the system controller 10 to the recording signal generator 21.Hence, the pulse duration and the pulse level can be adjusted. This isadvantageous for performing appropriate recording.

According to the embodiment described above, the end overdrive pulse andthe first overdrive pulse are added to the EQEFM signal, therebygenerating the driving current i. Hence, the laser emission control asshown in FIG. 3 is performed. The recording signal generator 21 adjuststhe EQEFM signal, the end overdrive pulse, and the first overdrive pulseso that the level and the pulse width thereof are varied in accordancewith the corresponding recording conditions and the pit length and theland length immediately before and after each pulse. The pulse width isarbitrarily and variably set in accordance with each of 3 T to 11 T.Accordingly, satisfactory writing is performed even at, for example, a×8 writing speed.

FIGS. 10 and 11 show measurements of the writing laser power and pitjitter characteristics and the writing laser power and land jittercharacteristics, respectively, when writing is performed at a ×8 speedusing a disk on which a cyanine-based organic dye film is formed. Inthis case, a value corresponding to the level Pod in FIG. 3 is obtainedby increasing the writing laser power Pw by 30%.

Referring to FIGS. 10 and 11, symbols i and ii indicate characteristicsobtained by performing laser power control by using the methods shown inFIGS. 14 and 15, respectively. Characteristics obtained by using a laserpower control method of the embodiment are indicated by iii.

The level of 35.0 nsec indicated by broken lines is the allowable limitof the jitter value.

FIGS. 12 and 13 show measurements of the writing laser power and pitjitter characteristics and the writing laser power and land jittercharacteristics, respectively, when writing at a ×8 speed is performedusing a disk on which a phthalocyanine-based organic dye film is formed.In this case, a value corresponding to the level Pod in FIG. 3 isobtained by increasing the writing laser power Pw by 25%.

It can be concluded from the measurement results shown in FIGS. 10 to 13that, independent of the material of the organic dye film, the pitjitter and the land jitter in the. embodiment indicated by iii aresignificantly improved compared with i and ii. In addition, a jitterpower tolerance on the writing laser power is greatly improved.

Specifically, it can be understood that the laser power control of theembodiment is suitable for writing at a fast rate, such as a ×8 writingspeed.

The embodiment is described hereinabove. Various modifications can bemade to the examples of the driving pulse waveform patterns for formingthe pits, the recording conditions for variably setting the pulseduration and the level, the set values, and the like.

1. A recording apparatus, comprising: laser means for performing laserbeam irradiation with a supplied driving pulse to form a recording datarow on a recording medium, said data row being formed of pits and lands,the lands being between the pits and the pits being before and after thelands; driving pulse generating means for generating pulses inaccordance with recording data, said pulses having a reproducing powerlevel, a first recording power level, and a second recording power levellarger than the first recording power level, said second recording powerlevel provided before and after the first recording power level; andpulse generation control means for controlling at least one of thepulses having the second recording power level generated by said drivingpulse generating means so that a pulse width thereof is varied inaccordance with a length of at least one of a pit and a land to beformed.
 2. The recording apparatus according to claim 1, wherein saidpulse generation control means further comprises means for variablysetting, in accordance with a predetermined recording condition, thesecond recording power level.
 3. The recording apparatus according toclaim 1, wherein said pulse generation control means further comprisesmeans for variably setting, in accordance with the length of at leastone of the land immediately formed before, the pulse width of at leastone of the pulses having the second recording power level.
 4. Therecording apparatus according to claim 1, further comprising: detectingmeans for detecting a length of a land immediately formed before the pitto be formed, wherein said pulse generation control means varies thepulse width of at least one of the pulses having the second recordingpower level in accordance with the detected land length.
 5. Therecording apparatus according to claim 4, wherein said detecting meansdetects a length of a pit immediately to be formed after the land; andsaid pulse generation control means varies the pulse width of at leastone of the pulses having the second recording power level in accordancewith the detected pit length.
 6. A recording method, comprising:generating a laser beam to form a recording data row on a recordingmedium, said data row being formed of pits and lands, the lands beingbetween the pits and the pits being before and after the lands; andmodulating the laser radiation to have a reproducing power level, afirst recording power level, and a second recording power level largerthan the first recording power level, said second recording power levelprovided before and after the first recording power level, wherein awidth of the second recording power level is controlled so that thewidth is varied in accordance with a length of at least one of a pit anda land to be formed.
 7. The recording method according to claim 6,wherein said generating step comprises selectively not generating thesecond recording power level in accordance with a speed at which saidrecording data row is formed on the recording medium.
 8. The recordingmethod according to claim 6, wherein said generating step comprisesvariably setting, in accordance with a predetermined recordingcondition, each of the first and second recording power levels.
 9. Therecording method according to claim 6, wherein said generating stepcomprises variably setting, in accordance with a predetermined recordingcondition, the width of the second recording power level within a rangeof 0 T to 3 T.
 10. A recording apparatus, comprising: a laser suppliedwith a driving pulse to form a recording data row on a recording mediumusing laser beam irradiation, said data row being formed of pits andlands, the lands being between the pits and the pits being before andafter the lands; a laser driver for generating the driving pulse inaccordance with recording data, said driving pulse having a producingpower level, a first recording power level, and a second recording powerlevel larger than the first recording power level, said second recordingpower level provided before and after the first recording power level;and a pulse generation controller for controlling a width of the secondrecording power level to be generated by said laser driver so that thepulse width thereof is varied in accordance with a length of at leastone of a pit and a land to be formed.
 11. The recording apparatusaccording to claim 10, wherein said pulse generation control means isconfigured to set the level of the second recording power level inaccordance with a predetermined recording condition.
 12. The recordingapparatus according to claim 10, wherein said pulse generationcontroller is configured to set the pulse width of at least the pulse ofthe second recording power level, in accordance with a length of atleast one of the land immediately formed before.
 13. The recordingapparatus according to claim 10, further comprising: a detectorconfigured to detect a length of the land immediately formed before apit to be formed, wherein said pulse generation controller is configuredto vary the pulse width of at least the pulse having the secondrecording power level in accordance with the detected land length. 14.The recording apparatus according to claim 13, wherein said detectordetects a length of the pit immediately to be formed after the land; andsaid pulse generation controller is configured to vary the pulse widthof at least the pulse having the second recording power level inaccordance with the detected pit length.